1. Field of the Invention
The present invention relates to a magnetic tape cassette. More particularly, it relates to a structure of a pad support member placed in an opening for inserting a head.
2. Description of the Prior Art
As shown in FIG. 1, a pad (4) is usually placed along a running direction of a magnetic tape (3) in an opening for inserting a head which is formed in the middle of a cassette casing (1) in a conventional magnetic tape cassette. The pad (4) is usually formed by bonding a buffering element (6) made of an elastic material such as a urethane foam on a surface of a pad support member (5) as a resilient plate made of a metal alloy such as phosphor bronze or, nickel silver. The magnetic tape (3) is pushed on a recording and reproducing head (7) under the resilient force of the pad support member (5) and the buffering force of the buffering element (6) to operate read-out and write-in of magnetic record. The references (8) and (9) respectively designate stems for holding the pad support member (5) and the stems are projected from an inner surface of the cassette casing (1). A magnetic shield plate (10) is placed to cover the pad support member (5).
When the pad support member (5) is prepared by punching a plate made of phosphor bronze or nickel silver, the plate is easily oxidized in air to form rust. Certain panel characteristics deteriorate and mechanical strength deteriorates to cause damage on the surface of the magnetic tape (3) and to remarkably decrease reliability. A magnetic tape cassette is often exposed to an environment of high temperature and high humidity as it is used as a car stereo tape cassette which has come into wide use. Therefore, it is important to prevent rusting of the pad support member. It has been considered to plate a metal on the pad support member, however it causes high cost and change of mechanical characteristics especially spring characteristic of the pad support member.